Dissipation limiter - energy saving circuit

ECG = electrocardiogram, EMG = electromyogram and EEG = electroencephalogram. All these "grams" deal with measurement and display of electric voltages being produced by the heart beat (ECG), the muscular activity (EMG) and brain activity (EEG). The heart "supplies" the strongest signals and the brain the weakest (didn"t we all know that?!) Many microprocessor enthusiasts may have had some thoughts of performing physical tests by means of their computer. Unfortunately no suitable interface has been avail- able ... until now; this circuit solves that particular problem. Three copper plates are used as electrodes. They are connected via screened cable to the differential amplifier which forms the input of the circuit. The circuit concsisting of Al ... A3 can also be described as an "instrumentation amplifier"; a differential amplifier with opamps and two high impedance inputs. The output signal of this input stage is filtered by the active low-pass filter A4 before being fed to the "...